Dangerously Hot Temperatures Cover a Large Portion of the U.S. This Weekend

Tom Moore
Published: July 23,2016
A massive dome of high pressure in the upper atmosphere is gripping a significant portion of the nation, providing favorable conditions for dangerously hot temperatures through this weekend.

Current "Feels Like" Temperature

In parts of the central U.S., heat index values will be up to 115 degrees at times. The heat will also spread toward the Northeast and mid-Atlantic over the weekend.
Hot temperatures are also pushing into the Southwest, including southern California.
The National Weather Service has issued heat alerts for 25 states in parts of the central, southwest and eastern states.

Heat Alerts

(MORE: Check the Forecast for the Next 10 Days)
Here's a look at what to expect through the weekend.

Sweltering Days Ahead

Central States
In addition to the hot temperatures, heat indices – a measure of how hot it feels – will be dangerously high with values in the 105- to 110-degree range in some locations.
(MORE: What is the Heat Index?)

Forecast Maximum Heat Index Sunday

For example, cities like St Louis, and Dallas, will see highs from the mid 90s to near 100 degrees Sunday with heat indices well above 100 degrees. Low temperatures will be in the 70s, providing not much relief at night.
The heat will extend into the mid-Atlantic region and down to the Carolinas with heat indexes expected to be 100 to 105 degrees.
(MORE: Four Things Extreme Heat Does to Your Body)
Relief from the extreme heat may arrive in parts of the Midwest and Great Lakes by early next week when temperatures return closer to average.
(MORE: Forecast Temperature Maps)

Forecast Highs

Eastern States
The ridge of high pressure will nudge its way into the Northeast. This will allow very hot temperatures to engulf parts of the Northeast and mid-Atlantic regions. Some daily record high temperatures will be within reach.
Washington D.C. and Philadelphia may see highs in the upper 90s to near 100 degrees through Monday. Highs in the middle to upper 90s are expected in New York City on Monday and Tuesday.
If Washington, D.C. hits 100 degrees, it would be the first time that's happened there since July 2012.
(MORE: Heat is the Deadliest Kind of Weather)

Forecast Highs

Southwest Heat
The southwestern states will also heat up through this weekend as the dome of high pressure spreads its wings toward that region of the country.
Highs in the 90s are likely in the Los Angeles metro area through this weekend.
Across the interior of Southern California and into southern Nevada and Arizona, expect readings to top 110 degrees.
Heat could even linger throughout the night in some locations due to downslope winds.

Southwest Weekend Forecast Highs

Reports: 
Except for the Pacific Northwest all other states, in the Lower 48, had at least one location reporting a temperature of 90 degrees or above on Friday afternoon.
The heat index at Memphis, Tennessee, reached 114 degrees on Friday afternoon while up in Sioux Falls, South Dakota it felt like 110 degrees.
Dallas reached 100 degrees on Friday for the first time this year, and then reached 100 degrees again on Saturday.
On Thursday, the heat index at Cedar Rapids, Iowa, topped out at an extremely dangerous 116 degrees.
Waco, Texas, recorded its first 100-degree day of the year on Wednesday. The average date for Waco's first 100-degree day is July 4, so this came over two weeks later than average. Dallas reached 100 degrees on Friday for the first time this year.

Heat Safety Tips

The hot conditions this week will be particularly dangerous for vulnerable groups such as the sick and the elderly. The National Weather Service offered useful heat safety tips that can be incorporated into a daily routine when extreme heat sets in.

• Job sites: Stay hydrated and take breaks in the shade as often as possible.
• Indoors: Check up on the elderly, sick and those without air conditioning.
• In vehicles: Never leave children or pets unattended – look before you lock.
• Outdoors: Limit strenuous activities and find shade. Drink plenty of water and avoid alcohol.

Massive high pressure ridge aloft is responsible for widespread heat across much of the U.S.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Atmospheric Heat Dome

So far this summer, there have been a couple of high-pressure ridges aloft (bulges in the jet stream) that have prevailed across the U.S. One ridge was positioned around the Western U.S., and the other was in the Southeast. The Western ridge has occasionally expanded a bit to the north and east, while the Southeast ridge has expanded north and west, but only for short periods of time.
A bridging of these ridges occureed late this week, resulting in one massive dome of high pressure. Beneath this dome, air sinks and warms, resulting in hot temperatures.
Under these conditions, thunderstorm activity has become sporadic, so many areas have been dry.
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